Imaging technique may help guide surgeons to remove malignant tissue

Scientists have developed a technique that can produce images of subcutaneous melanomas, according to a study published in ACS Nano (2010 Aug 24;4(8):4559-64).

Led by Lihong Wang, PhD, the Gene K. Beare Distinguished Professor of Biomedical Engineering, and Younan Xia, PhD, the James M. McKelvey Professor of Biomedical Engineering, researchers combined an imaging technique with a contrast agent to produce detailed three-dimensional images.

The imaging part of the technique, developed by Dr. Wang, is based on the photoacoustic effect which involves converting sound to light, transmitting the light, and then converting it back to sound at a receiver. “We detect the sound signal outside the tissue, and from there on, it's a mathematical problem,” Dr. Wang explained. “We're essentially listening to a structure instead of looking at it.”

The contrast agent used with the technique, developed by Dr. Xia, helped to create photoacoustic images of biological tissue. For the study, Dr. Xia injected the malignant tissue with gold to help improve the contrast between the malignant and normal tissue. Once injected, Dr. Xia explained that the gold particles naturally tended to accumulate in tumors because the cells that line a tumor's blood vessels are disorganized and leaky. However, Dr. Xia's team dramatically increased the uptake rate by decorating the nanoparticles with a hormone that binds to hormone receptors on the melanoma's cells.

The study's findings revealed that in experiments with mice, melanomas took up four times as many “functionalized” nanocages than those nanocages coated with an inert chemical. Furthermore, with the contrast agent, the photoacoustic signal from the melanoma was 36% stronger.

The scientists stated that subcutaneous mouse melanomas barely visible to the unaided eye show up clearly in photoacoustic images, with their subterranean peninsulas and islands of malignancy starkly revealed.